For bees living in the 21st century, the world is a dangerous place. With grasslands being increasingly converted into corn and soybean fields, finding wild flowering trees, weeds and other plants can be a challenge.
In Oslo, Norway, residents, government and business owners have added flowering plants to terraces and city squares, creating, in essence, a "bee highway" that bees can use to make their way through the otherwise heavily urbanized city.1
Oslo's bee highway is the first of its kind, and bees in other areas of the world may not be so lucky. In the U.S., for instance, bees often live near genetically engineered (GE) corn and soybean fields.
These seeds are often coated in neonicotinoid pesticides, and the chemicals are found in corn and soybean pollen.
Neonicotinoids have been blamed as one culprit in declining bee populations in the U.S. and elsewhere. However, perhaps the bees have a sixth sense, because they don't feed much on the GE corn and soy. Instead, they look for flowering plants nearby.
Unfortunately, this raises its own set of risks. Research published in the journal Nature Communications revealed that pollen collected next to corn fields is contaminated with up to 32 different pesticides.2
Bees May Be Exposed to 32 Pesticides When Collecting Pollen
When the researchers started their study, they expected to find neonicotinoid pesticides in pollen collected by foraging honey bees. They explained:
"Recent efforts to evaluate the contribution of neonicotinoid insecticides to worldwide pollinator declines have focused on honey bees and the chronic levels of exposure experienced when foraging on crops grown from neonicotinoid-treated seeds.
However, few studies address non-crop plants as a potential route of pollinator exposure to neonicotinoid and other insecticides.
Here we show that pollen collected by honey bee foragers in maize- and soybean-dominated landscapes is contaminated throughout the growing season with multiple agricultural pesticides, including the neonicotinoids used as seed treatments."
There were two surprises, however. First, pollen from crop plants made up only "a tiny fraction" of the total pollen collected by the local bees. Second, the highest levels of contamination in pollen came from pyrethroid insecticides, which are often used as repellents for mosquitoes and other household pests.
Both phenothrin, used to repel ticks and fleas, and prallethrin, used primarily for targeting wasps and hornets, were detected in the pollen, as were up to 32 different pesticides in all (most of which are not used for agricultural applications).
The research highlights the fact that even household and commercial use of insecticides may be contributing to bee die-offs. For instance, the common mosquito repellent DEET (N,N-diethyl-meta-toluamide) was found in every pollen sample.
Bees Exposed to Chemical Cocktails
Many pesticides are water-soluble, which means they probably end up in pollen after mixing with water and being absorbed via the plants' roots. Some are also likely sprayed directly onto plants.
DEET, however, is fat-soluble. Since it doesn't mix with water, researchers don't know how the chemical is ending up in pollen, especially with such regularity. Unfortunately, the study revealed significant pesticide contamination in the pollen tested.
Researcher Christian Krupke, Ph.D., an entomology professor at Purdue University, told Newsweek, "At no time did we find only one or two or three pesticides — we found multiple pesticides co-occurring in every single sample."3
Yet, researchers typically study the effects of only one chemical at a time. What happens with exposure to chemical cocktails, which is a more realistic snapshot of what bees are actually facing, is a mystery. Krupke continued, "You can imagine that if you have many at a time, you could have enhanced toxicity."4
The study is in line with a 2013 study, in which researchers analyzed pollen from bee hives in seven major crops and found 35 different pesticides along with high fungicide loads.5 Each sample contained, on average, nine different pesticides and fungicides.
When the pollen was fed to healthy bees, they had a significant decline in the ability to resist infection with the Nosema ceranae parasite, which has been implicated in bee deaths. In all likelihood, it's not one or two chemicals that are the problem but many.
New Neonicotinoid Research Shows How the Chemicals Harm Bees
The majority of soybean, corn, canola, and sunflower seeds planted in the U.S. are coated with neonicotinoid pesticides (neonics). The chemicals, which are produced by Bayer and Syngenta, travel systemically through the plants and kill insects that munch on their roots and leaves.
Neonicotinoids are powerful neurotoxins and are quite effective at killing the pests, but they're also harmful to non-target pests, namely pollinators such as bees and butterflies.
This occurs because the pesticides are taken up through the plant's vascular system as it grows, and as a result, the chemical is expressed in the pollen and nectar of the plant.
Until now, the effects of different neonicotinoids have been regarded as interchangeable, but a new study showed each may affect bees differently. Bayer's imidacloprid was found to cut the number of egg-containing brood cells by 46 percent.
Syngenta's thiamethoxam, on the other hand, decreased the number of live bees by 38 percent.
Clothianidin, another neonicotinoid made by Bayer, had the curious effect of increasing the number of queens produced, which the researchers noted could potentially backfire if, "say, all those queens turned out to be infertile."6,7
Lead researcher Christopher Connolly, Ph.D. of the University of Dundee told the Guardian, "I think there is sufficient evidence for a ban on imidacloprid and thiamethoxam … "8